Does fine-tuning a chatbot make it more brain-like? We checked
There is a popular idea that a language model's internals line up with activity in the human brain. We asked whether the fine-tuning that turns a raw model into a helpful chatbot strengthens that match. The fine-tuning itself does not change the match. What looked like a change came from how the text was formatted on the way in.
When a person reads a sentence, specific parts of their brain light up, and you can measure it with an fMRI scanner (a brain scanner that tracks blood flow as a stand-in for activity). When a language model reads the same sentence, specific patterns of numbers light up inside the network. Over the last few years, researchers have found something striking: if you fit a simple translator from the model's internal numbers to the brain's activity, it predicts the brain better than chance. The model and the brain are not identical, but they line up better than chance.